Process for the cross-linking of polyolefins and for the vulcanization of rubber



United States Patent 3,267,066 PROCESS FOR THE CROSS-LINKING 0F POLYOLE- FINS AND FOR THE VULCANIZATION 0F RUBBER Stephanus Bernardus Tijssen, Deventer, Netherlands, assignor to Koninklijke Industrieele Maatsehappi Voorbeen Noury 8; van der Lantle N.V., Deventer, Netherlands No Drawing. Original application June 2, 1961, Ser. No. 114,320. Divided and this application Aug. 20, 1964, Ser. No. 412,270 Claims priority, application Great Britain, June 8, 1960, 20,154/60 1 Claim. (Cl. 260--41) The present invention relates to a process for crosslinking as well as vulcanisation of natural and synthetic rubbers with the aid of the ditertiary peroxides prepared by the process according to the present invention.

This application is a division of my co-pending application Serial No. 114,320, filed June 2, 1961, and now abandoned.

The process for the preparation of ditertiary peroxides in accordance with the present invention comprises effecting reaction in the presence of an acid reacting compound, between equimolar quantities of (l) a tertiary hydroperoxide and (2) a compound selected from the group consisting of (a) compounds represented by the general formula R C=C\ R, R, and (b) compounds represents by the general formula R1 R3 R3 R1 I l c=c-A-o=c R R wherein each R and R is selected from the group consisting of hydrogen, alkyl, cycloalkyl, and aryl and each R and R is selected from the group consisting of alkyl, cycloalkyl and aryl and A represents a hydrocarbon group having up to 6 carbon atoms and may be aromatic or aliphatic.

The tertiary hydroperoxide The tertiary hydroperoxide used as one of the starting materials in the preparation of the organic peroxides according to the present invention may be an aliphatic tertiary hydroperoxide such as a tertiary alkyl hydroperoxide e.g. tertiary butyl hydroperoxide or tertiary amyl hydroperoxide; or a cycloalkyl hydroperoxide such as pararnenthane hydroperoxides or an aralkylhydroperoxide such as cumylhydroperoxide. Furthermore halogenated derivatives of the above groups of compounds may be used in their stead, as for example 1-chloro-Z-methyI-Z-hydroperoXy-propane and 1,1-dichloro'2-methyl-2 hydroperoxypropane.

The unsaturated olefinic compound The tertiary hydroperoxide described above is reacted with a suitable olefinic compound of the type described above wherein (b) is merely a specific species of (a) in which R has the significance of Suitable olefinic compounds for reaction with the tertiary hydroperoxide include amongst others alpha methylstyrene, parachloro-alpha methylstyrene, diisopropenylbenzene, diisobutylene, 2,5-dimethyl-hexadiene-1,5- and dipentene. The above list of compounds is merely illustrative of the compounds which may be used is not intended to be construed as limiting the invention to the particular compounds mentioned.

The reaction between the tertiary hydroperoxide and the olefinic compound, which can best be accomplished in an anhydrous medium, is suitably carried out at a temperature of about l080 C., preferably however at a temperature of 4050 C. or at a temperature slightly be low the decomposition temperature of the peroxide concerned.

The reaction is catalyzed by small quantities of both inorganic or organic acid-reacting compounds, such as perchloric acid, sulphuric acid, borontrifluoride, hydrogenchloride, hydrogenbromide, para-toluenesulphonic acid, benzene sulphonic acid and meta-benzenedisulphonic acid.

If the catalyst to be used is not soluble in the reaction medium or is soluble only to a small extent, the reaction is preferably performed in the presence of aliphatic monocarboxylic acids, such as acetic acid.

If para-toluene sulphonic acid is used as a catalyst, 0.1-10.0 g. (respectively 0.1-4.0 g.) per mole of peroxide will usually sutlice. If the catalyst is HCl, 0.1-4.0 g. per mole of peroxide will be found suflicient.

The ditertiary peroxide produced as a result of the reaction is readily recovered from the reaction mixture by washing the reaction mixture with an alkali and then washing it free of alkali. The mixture is then dried and then any volatile impurities are eliminated by vacuum distillation at temperatures below those at which the product distills over.

In order that the invention may be readily understood by those skilled in the art, the following specific examples are given by way of illustration.

Example I.Preparati0n of cumyl-terliary butylperoxide 24.0 g. of technical tertiary butylhydroperoxide (0.2 mole) were mixed with 23.6 g. of alpha-methylstyrene (0.2 mole). Thereafter, a solution of 0.4 g. of perchloric acid (0.004 mole) in 20 ml. of glacial acetic acid was added to the mixture.

The reaction mixture was heated with stirring at a temperature of 40 C. for 6 hours.

In order to isolate the cumyl-tertiary butylperoxide formed, the reaction mixture was washed with 1 N NaOH and subsequently freed from alkali with water. Thereafter the volatile impurities were eliminated at a pressure of 15 mm. and subsequently at a pressure of 1 m at a temperature of 60 distilled over.

20.8 g. of cumyl-tertiary butylperoxide with a boiling point of 40 C. at 0.1 mm., were obtained. N =l.4803.

The preparation was repeated using 1.52 g. of paratoluene sulphonic acid (0.008 mole) instead of the solution of perchloric acid in glacial acetic acid. On heating the reaction mixture at a temperature of 45 C. for 20 hours, 32.5 g. of cumyl-tertiary butylperoxide was obtained.

m. and C., after which the product was Example H.Preparati0n 0f dicumylperoxide cumylhydroperoxide (0.2

of 15 mm. and subsequently at a pressure of 0.1 mm. and at a temperature of 90 C., after which the product was cooled.

30.2 g. of dicumylperoxide (90%) were obtained.

Example III.Preparatin of cumyl-tertiary butylperoxide 3.65 g. (0.1 mole) of dry hydrogen chloride were brought into 135.7 g. (1.15 mole) of alpha-methylstyrene. Subsequently 92 g. of tertiary butylhydroperoxide (98%) (1 mole) were added, after which the mixture was heated with stirring at a temperature of 50 C. for hours.

In order to isolate the cumyl-tertiary butylperoxide formed, the reaction mixture was washed with 4 N NaOH and subsequently freed from alkali with water.

, After drying on anhydrous potassium carbonate the volatile impurities were eliminated and subsequently the cumyltertiary 'butylperoxide was distilled off at a pressure of 0.25 mm. and at a temperature of 42 C.

148 g. of cumyl-tertiary butylperoxide were obtained. N =1.4800.

Example I V.Preparati0n of dicumylperoxide 1.82 g. (0.05 mole) of dry hydrogen chloride were brought into 129.8 g. (1.1 mole) of alpha-methylstyrene. Subsequently 217 g. of cumylhydroperoxide (70%) (1 mole) were added, after which the mixture was heated with stirring at a temperature of 40 C. for 5 hours.

In order to isolate the dicurnylperoxide formed the reaction mixture was washed with 4 N NaOH and subsequently freed from alkali with water.

Thereafter the volatile impurities were eliminated at a pressure of mm. and subsequently at a pressure of 1 mm. and at a temperature of 95 C., after which the product was cooled. 182 g. of dicuinylperoxide (98.2%) were obtained.

Example V.Preparati0n of 2-(t-batylper0xy)-2,4,4-

trimethylpentane 112 g. (1 mole) of diisobutylene were mixed with 91 g. of tertiary butylhydroperoxide (99%) (1 mole). Subsequently 7.6 g. (0.04 mole) of crystallised paratoluenesulphonic acid were added to this mixture with stirring, while the temperature raised to 40 C. The mixture was maintained at this temperature for 4 hours.

In order to isolate the product formed the reaction mixture was washed with 4 N NaOH and subsequently freed from alkali with water.

After drying on anhydrous sodium sulphate the volatile impurities were distilled in vacuo after which 52 g. of 2-(t-buty1peroxy)-2,4,4trimethylpentane were obtained by distillation. Boiling pt. 45 C./ 3 mm. Hg.

Cale2r612ated Found 199 M01. weight-Analysis Percent Percent Percent G H 0 Found 0. 6 12. 8 16.6 Calculated 71. 3 12.8 15. 9

Example VI .--Preparati0n of 2,5-di tertiary butylperoxy)-2,5-dimethyllzexane in vacuo after which 15.2 g. of 2,5-di(tertiary butylperoxy)-2,5-dimethylhexane were obtained by distillation. Boiling pt. 42 C./0.060.07 mm. Hg. N =1.4210.

Example VlL-Preparation 0f I,4bis(tertiary butylperoxyisopropyl) benzene 174 g. 1.1 mole) of para-diisopropenylbenzene were dissolved in benzene whereafter 0.2 mole (7.3 g.) of dry hydrogen chloride were introduced. Subsequently 184 g. of tertiary butylhydroperoxide 98% (2 moles) were added, after which this mixture was heated to 50 C. for 5 hours with stirring. The reaction mixture was washed with 4 N NaOH and subsequently freed from alkali with water. After drying on anhydrous potassium carbonate the benzene was distilled off and the product obtained was recrystallised, after which 237 g. of 1,4 'bis( tertiary butylperoxyisopropyl) benzene were obtained.

Melting pt. 79 C. Molecular weight: found 331, calculated: 338.

Elementary analysis.Found C, 70.6%; H, 10.2%, 0, 19.2%. Calculated C, 71.0%; H, 10.1%, 0, 18.9%.

Example VIII.-Vulcanisati0n of ethylene/propylene c0- polymer with 1,4 bis(tertiary butylperoxyisopropyl) benzene 100 parts of an ethylene/ propylene copolymer containin 40 mole percent of propylene were mixed on mixing rolls with 50 parts of HAF carbon black and 3 parts of 1,4 bis(tertiary butylperoxyisopropyl)benzene, prepared in the preceding example.

The resulting mixture was vulcanised in a press at 160 C. for 30 minutes. i

The mechanical properties of the vulcanised product are comparable to those obtained with 4 parts of dicumylperoxide under essentially the same conditions. The effect of the addition of sulphur in a quantity of about 1% is the same in both cases.

The reduced quantity of 1,4 bis(tertiary butylperoxyisopropyl)benzene, necessary to obtain satisfactory results may be accounted for by the fact that this perioxide contains two peroxide groups instead of one.

Example IX.-Vulcanisati0n of natural rubber with 1,4 bis(tertiary batylperoxyisopropyl)benzene 100 parts by weight of natural rubber (smoked sheets) were compounded on a rubber mill with 50 parts by weight of. furnace black and 1.5 parts by weight of 1,4 bis(tertiary butylperoxyisopropyl)benzene. The rolls of the mill were maintained at about C.

After thoroughly mixing the sheet was cured at 150 C. for 30 minutes. The tensile strength of a product prepared in this way is well above 2,000 p.s.i. and its general properties are virtually the same as those obtained by using 2.5 parts by weight of dicurnyl peroxide.

I claim:

A process for vulcanizing polymers selected from the group consisting of polyolefins and natural rubber comprising mixing about parts by weight of the polymer to be vulcanized with up to 50 parts by weight of carbon black and about 3 parts by weight of a catalyst consisting essentially of Z-tertiary butyl-peroxy-2,4,4 trimethylpentane.

References Cited by the Examiner UNITED STATES PATENTS 3,118,866 1/1964 Gregorian 26094.9 3,129,204 4/1964 Gilmont 2606l0 3,135,805 l/1964 Gilrnont 260610 OTHER REFERENCES Davies et al.: Chem. Soc. Iour. (London), pages 2200- 2204 (1954).

MORRIS LIEBMAN, Primary Examiner. A. LIEBERMAN, Assistant Examiner. 

